The invention relates to a method of tuning and compensating power levels in a radio telephone having a logic section which controls the operation, and to the use of this method in series production and maintenance. The invention also relates to a radio telephone, which is tuned with a method according to the invention.
Generally the power levels in a radio telephone are tuned by adjusting built-in trimmer potentiometers and monitoring the output power of the radio telephone. The tuning is generally made manually, although in some cases a tuning with the aid of robots could be possible. It is however common to these prior art methods to adjust electromechanical components, such as trimmer potentiometers, with the aid of tools.
The power of the transmitter may vary with the operating conditions of the radio telephone. The operating conditions are influenced by the selected channel frequency, the radio telephone's internal temperature and the supply voltage (accumulator or battery voltage). In prior art it is generally tried to compensate for the power variations with means of analog technology. Diodes or NTC resistors are used to compensate for power variations due to temperature changes, for example. The transmitter output power of individual radio telephone units can behave in very different ways at various temperatures and with various voltages, and thus the compensating circuitry designed for a radio telephone type does not necessarily function in a desired manner for every unit in series production.
The known methods entail many problems and drawbacks. The trimmer potentiometers, being electromechanical components, are less reliable than the electronic components used in the radio telephone and they take up a substantial area on the device's circuit board. The need for a large space is a problem, particularly concerning handsets. In addition, tuning of the trimmers is slow and requires a skilled person performing the tuning. The tuning precision depends on the person, and thus human errors are possible. The radio telephone casing has to be opened for the tuning in order to get access to the various components.
The power levels are usually compensated for temperature and battery voltage variations by analog techniques, so that the accuracy of the compensation depends on component tolerances, and a fully individual compensation will not be possible in series production.
The object of the invention is to devise a method, with which the above mentioned prior art problems and drawbacks are obviated. The solution to the problem is achieved in accordance with my invention wherein external tuning equipment is connected to the radio telephone's antenna interface and at least one auxiliary interface. The tuning equipment measures the power level delivered by the transmitter to the antenna interface and this power level is adjusted until the desired power level is achieved. In accordance with an aspect of my invention, the individual tuning results are then stored as compensating values in a non-volatile memory in the radio telephone whereby in operation the transmitter's power level is controlled according to these stored tuning results.
In the invention it is essential to store individual tuning results for chosen operating conditions into the radio telephone's memory as compensating values. Specifically in one embodiment of my invention the transmitter's respective power level is controlled in accordance to the tuning results by the logic section via a D/A-converter when the radio telephone is in operation. Preferably the tuning is made by connecting the tuning equipment to the normal external connections of the radio telephone, the tuning being made without opening the radio telephone casing.
This tuning arrangement may be applied to the final testing in series production of radio telephones, and to the maintenance of radio telephones.
The radio telephone according to the invention includes sensors connected to the logic section and detecting the radio telephone's operating conditions, and between the logic section and the transmitter a D/A-converter is arranged, which converts data corrected with compensating constants and output by the logic section into a voltage controlling the transmitter power.